As mentioned before, there are only ten localized FRBs [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, which means the redshifts for most FRBs are unknown. Assuming that the accurate \(DM_{\rm IGM}\)  is known, we check whether the redshift of FRB can be precisely derived from the \(z-DM_{\rm IGM}\)  relation.
